1. SiSPAT-Isotope model Better estimates of E and T Jessie Cable Postdoc - IARC

2. Very green landscapes that are fluxing water to the atmosphere

3. http://www.marietta.edu/~biol/biomes/imag es/wetlands/sphagnum_6449a_A80.jpg Transpiration Evaporation Transpiration = Plants control the water vapor flux Evaporation = mosses are an evaporating surface (BUT, they are NOT bare ground) - Combination of vascular and non-vascular plants - Different water flux dynamics necessitate distinguishing between them (E and T vs. ET)

5. Need better assessment of E and T Need more accurate representation of E and T in atmosphere, hydrological, or vegetation growth models Tape et al. 2006 CREW-NASA ET Rainfall recycling and watershed/soil water balance Changes in landscape / vegetation distributions impact magnitude and partitioning of ET

6. Little data exist to validate the partitioning of E and T in SVAT (Soil Vegetation Atmosphere Transfer) models Concentration measurements of stable isotopes of water in soil, plants, and vapor can aid in partitioning / quantifying E and T –E and T differentially impact concentration of isotopes in soil or vapor soil stable isotope concentrations useful for –determining plant rooting profiles (for validation of root extraction submodels in SVAT) –better quantification of water transfer within soils (vapor diffusion coefficients and hydraulic properties) 1 H, 2 H 16 O, 18 O H2OH2O

7. SiSPAT-Isotope model Braud et al., Journal of Hydrology 309 (2005) 277-300, 301-320 Modification of the pre-existing 1D SiSPAT model (Simple Soil Plant Atmosphere Transfer model) to include transport of stable isotope species to better estimate E and T Coupled heat, water, and isotope transport equations solved for temperature and matric potential and isotope profiles forced by air temp, humidity, wind speed, incoming solar and long wave radiation, rainfall bare ground, saturated soils, steady state conditions (equilibrium between vapor and liquid phases for isotopes) Currently focused on estimating kinetic fractionation coefficient

8. Issues with adding isotope transport Correctly accounting for fractionation associated with molecular diffusion turbulent vs molecular diffusion affecting resistance to isotope vapor flux Need a plant component and proper treatment of plant physiology Kinetic fractionation factor for drying soils and non-saturated conditions 1 H, 2 H 16 O, 18 O

9. Data-model integration issues The solution of the isotope species transport equation requires high resolution of the vertical profile near the surface (particularly to capture the vapor return) Problem: require fine time steps that field sampling can not yet provide